How to sow hardy annuals in spring
Easily grown from seed, a vast choice of hardy annuals is available to offer long-lasting flowers during the warmer months. These fast-growing plants provide an easy and cost-effective way to give naturalistic planting, plug gaps and fill the border with a summer full of colour.
Difficulty Easy to moderate
Spring sowing is suitable for hardy annuals (plants which are sown, flower and die in one year) that tolerate light frosts. A spring sowing differs from an autumn sowing in that it tends to produce a later flowering display and the plants you can grow are not tough enough to survive the winter reliably. Seed catalogues often use the abbreviation (HA) to describe hardy annuals.
It should be noted that although these plants usually withstand frosty conditions without protection, some hardy annuals may need covering with horticultural fleece or a cloche when a heavy frost is forecast. Check the seed packets for full details.
Half hardy annuals need to be sown and grown on under glass or on a windowsill, being planted out only in late spring when there is no further risk of frost or the likelihood of cold weather.
Hardy annuals to try
The following are some suitable hardy annuals requiring no protection unless the winter is particularly severe:
Calendula officinalis (pot marigold): Slightly aromatic leaves and single or double daisy-like flowers in shades of orange or yellow flowers from summer to autumn. Height 45-60cm (18in-2ft) and spacing 30-37cm (1ft-15in).
Chrysanthemum carinatum (annual chrysanthemum): Tricoloured daisy flowers. Height 45-75cm (18-30in) and spacing 25-75cm (10–30in).
Clarkia amoena (godetia): Slender annuals with funnel or globe shape flowers in white, pinks, reds and salmon. Height 45-60cm (18in-2ft) and spacing 15-23cm (6-9in).
Cosmos bipinnatus: Tall, bushy plants with large daisy-like flowers in whites and pinks. Height 60-120cm (2-4ft) and spacing 37-55cm (15-22in).
Gypsophila elegans (baby's breath): Clusters of numerous tiny white or pink flowers on slender stalks in summer. Height 45-60cm (18in-2ft) and spacing 23-30cm (9in-1ft).
Helianthus annuus (sunflower): Classically yellow with a black centre but also in lemon, reds and browns. Height 60cm-3m (2-10ft) and spacing 60cm-1.2m (2ft-6ft).
Limnanthes douglasii (poached egg plant): Masses of dainty cup-shaped yellow-centred white flowers from summer to autumn. Height 15cm (6in) and spacing 15-18cm (6-7in).
Lavatera trimestris (tree mallow): Funnel shaped white or pink flowers. Height 75cm-1.2m (30in-4ft) and spacing 45-50cm (18-20in).
Matthiola incana (night-scented stocks): Highly perfumed pink or white flowers in spikes. Height 15-30cm (6in-1ft) and spacing 12-15cm (5-6in).
Tropaeolum majus (nasturtium): Sprawling or climbing easy-to-grow annual with yellow, orange or red edible flowers. Height 30cm-1.2m (1-4ft) and spacing 30-90cm (1ft-36in).
Agrostemma githago ‘Milas Purple Queen’ (corn cockle): With purple-red flowers. Height 75cm (30in) and spacing 40cm (16in).
Amaranthus caudatus (love-lies-bleeding): Blood-red pendant tassles, good as cut and dried flower. Height 60-130cm (2ft-51in) and spacing 45-50cm (18-20in).
Briza maxima (quaking grass): With creamy-white shimmering spikelets, ideal for dried arrangements. Height 60cm (2ft) and spacing 30cm (1ft).
Cerinthe major 'Pupurascens': With fleshy blue-green leaves and dark purple-blue flowers. Height 60cm (2ft) and spacing 30cm (1ft).
Coreopsis tinctoria 'Mardi Gras': Yellow starry flowers with red centre. Height 50cm (20in) and spacing 25cm (10in).
Echium vulgare 'Blue Bedder' AGM (viper's bugloss): Spikes of violet-blue flowers, magenta when fading. Height 30-45cm (1ft-18in) and spacing 40-45cm (16-18in).
Moluccella laevis (bells of Ireland): With fragrant green flowers are ideal for flower arranging. Height 90cm (3ft) and spacing 45cm (18in).
Nemophilia menziesii ‘Penny Black’: With masses of attractive deepest-purple flowers, edged white. Height 15-30cm (6in-1ft) and spacing 15-20cm (6-8in).
Nicandra physaloides (shoo-fly plant): With blue bell-shaped flowers and papery Chinese lanterns. Note - can become weedy. Height 90cm-1.2m (3-4ft) and spacing 45-60cm (18in-2ft).
Orlaya grandiflora: Has distinctive ferny foliage. Lacy pure-white flower umbels are ideal for flower arranging. Height 45-75cm (18-30in) and spacing 25-40cm (10-16in).
Phacelia (fiddleneck): Lavender to bright blue flowers in succession. Height 23-60cm (9in-2ft) and spacing 12-37cm (5-15in).
Salvia viridis (annual clary): Showy pink, purple or white leaf-like bracts in summer. Height 45-50cm (18in-2ft) and spacing 25-30cm (10in-1ft).
Xerochrysum bracteatum (syn. Helichrysum) (everlasting flower): Papery everlasting flowers suitable for drying. Height 45-75cm (18-30in) and spacing 25-30cm (10in-1ft).
Good for wildlife
As well as being ornamental, some hardy annuals will provide nectar and pollen for bees, butterflies and other insects. Phacelia tanacetifolia, viper's bugloss, pot marigolds, cornflowers and sunflowers are all suitable. Those with attractive seedheads such as Nigella and poppies can provide a valuable food source for birds.
For additional varieties, see our hardy annuals for autumn sowing page.
When to sow hardy annuals
Sowing can begin from late March to May as the soil begins to warm up (often indicated by the emergence of weed seedlings). It may begin earlier in milder gardens of the south and west; in colder northern gardens sowing may be later.
Annuals do best on light soils. These are not usually too fertile which and have the advantage over heavier soils, of warming up earlier in the spring. Germination is slower on heavier, poorly drained soils which remain colder for longer after winter.
Lush growth and fewer flowers may result on rich soils. It is worth noting, however, that cornfield annuals tolerate a richer soil and make a good alternative to a wildflower meadow where soil is too fertile.
How to sow seed
Weed the bed, level the soil with a rake and tread lightly before sowing.
Direct sowing can be done by broadcasting (scattering seeds over the surface). The main disadvantage of broadcasting is that you cannot easily tell weed seedlings apart from your sowings. Alternatively, drills (shallow grooves), can be planned and marked out to produce drifts of flower for a natural appearance.
Refer to seed packets for the best time to sow and depth for seed planting. Spacing between drills depends on the eventual size of the plants.
Once plants are growing strongly, attention will be needed to:
- Keep down weeds with light hoeing or hand weeding.
- Water in dry weather, regularly checking to ensure seed bed does not dry out during the early stages of germination and seedling establishment.
- Once well established, water at 10-14 day intervals during dry spells.
- Deadhead to prolong flowering.
- Thin out self-sown seedlings and transplant to fill gaps elsewhere in the garden.
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